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单选题
Which of the following phrases is allowed?
A
“when passing”+“significant point”+“climb/descent to”+“level”
B
“when passing”+“slot/time/significant point/level”+“contact”+“unit”+“frequency”
C
“when passing”+“level”+“resume normal climb/descent”
D
“when ready”+“climb/descent to”+“level”
答案解析
正确答案：C
